1. Field of the Invention
The invention relates to an optical disc drive and, more particularly, an adjusting mechanism comprising a cam-shaped adjusting base used to adjust the inclination of the optical pickup head of the optical disc drive.
2. Description of the Related Art
In an optical disc drive, an inclination between an optical pickup head 5 and an optical disc 7 usually causes a non-perpendicularity of the laser beam relative to the optical disc 7. If this inclination is excessive, it affects the correctness of the reading/writing operation on the optical disc, and more particularly digital audio-video optical discs for which the exactness is even stricter. Therefore, an adjusting mechanism is conventionally needed to adjust adequately this inclination to within an acceptable range.
As illustrated in FIG. 1 through FIG. 3, the adjusting mechanism as known in the art may be mounted on a principal guide rod 8 and a secondary guide rod 9 of the optical disc drive. The optical disc drive usually comprises a chassis 3 that supports an optical pickup head 5 for reading and writing data from an optical disc 7. A principal guide rod 8 and a secondary guide rod 9 are mounted parallel to each other on the chassis 3. The principal guide rod 8 and secondary guide rod 9 respectively lie along a lengthwise direction of the chassis 3. An end of the principal guide rod 8 is assembled with an attachment device 10 that comprises a fixing screw 11 an adjusting screw 12, a pressing plate 13, a spring 14 and an attachment base 15. One end of the principal guide rod 8 and two ends of the secondary guide rod 9 are respectively mounted between a pressing plate 13 and a spring 14 of one attachment device 10. The optical pickup head 5 is slidably mounted on the principal guide rod 8 and secondary guide rod 9 along which it is slidably driven by means of a driving motor 16a for performing reading/writing operation on the disc 7 placed on the spindle motor 16.
As illustrated in FIG. 3, the fixing screw 11, the adjusting screw 12, the pressing plate 13, the spring 14 and the attachment base 15 also conventionally form the adjusting mechanism. Each spring 14 is placed below a rod end for pushing upward the corresponding rod end. The attachment base 15 is fixedly attached via the fixing screw 11. The adjusting screw 12 engages through a pressing plate 13 over each corresponding rod end. Via the rotation of the adjusting screws 12, the respective inclination of the principal and secondary guide rods 8, 9 can be adjusted to obtain an adequate inclination of the optical pickup head 5.
However, a disadvantage of the above conventional structure is that the setting of an initial position before adjustment is not easily achieved. The adjustment therefore is too often performed blindly without any reference point. Furthermore, the amount of elements needed in the above adjusting mechanism is excessive and the assembly is relatively complex, which increase the production cost.